What size dehumidifier do I need?
Size a dehumidifier by your room's area and how damp it feels, in the current 2020 pint ratings. Those ratings read lower than old charts for the same machine, so a number from a pre-2020 chart will oversell you.
Dehumidifier size calculator
current 2020 pint ratingThis is a sizing estimate, and it is our own model. No clean current AHAM square-footage chart exists to copy, so we derive one from the current standard, shown on the size chart page. If you have persistent water or seepage, a bigger dehumidifier is not the fix: that is a drainage or foundation job for a pro. A sealed crawl space usually needs a dedicated crawl-space unit, not a portable.
Why the pint numbers dropped
In 2020 the federal test procedure moved the temperature it measures at from 80F down to 65F, which is much closer to the cool basements these units actually run in. Cooler air holds less water vapor, so a machine pulls fewer pints out at the test point. The machine did not get weaker; the label got more honest.
The practical effect: an old 70-pint unit is rated about 40 to 45 pints today, and the standard portable sizes are now 20, 30, and 50 pints instead of 30, 50, and 70. Most charts still floating around the web use the old numbers, which is how people end up buying more machine than they need. The size chart lays out the full old-to-new translation.
Common questions
What size dehumidifier do I need for a basement?
It depends on the area and how damp it is. A moderately damp basement around 1,000 square feet lands near a 30-pint unit in today's ratings; a wet basement the same size needs a 50-pint. Enter your square footage and pick the dampness that matches, and the tool gives a current-standard size. Basements are the case the 2020 test change was built around.
What size dehumidifier for a 1,000 sq ft basement?
Around a 30-pint unit if it is moderately damp, stepping up to a 50-pint if it is wet with moisture on the walls. These are the current (2020) pint ratings, which read lower than the old numbers for the same machine. If the space runs past what a 50-pint portable covers, a whole-home unit is the right class.
Is a 50-pint dehumidifier the same as it used to be?
No, and this trips people up. In 2020 the test point dropped from 80F to 65F, closer to a real basement. Cooler air holds less moisture, so the same machine now posts a lower pint number. A unit rated 70-pint before 2020 is rated about 40 to 45 pints today, not 50. We size in the current numbers so you buy the right machine.
Do I need a bigger dehumidifier for a wet basement?
A wetter space does need more capacity, and the tool steps the size up as you raise the dampness level. But if you have standing water or seepage, a bigger dehumidifier is not the answer. That is a drainage or foundation problem for a professional; a dehumidifier manages humidity, it does not stop water coming in.